We are seeing a lot of crown rot in paddocks this season. After a dry spring across much of southern Queensland and northern NSW, that is no surprise: crown rot can sit in a crop all season without showing, and it comes out when the crop runs short of water at the end. What carries into 2027 is the fungus left in your stubble, and you can measure it while that stubble is still standing. We are independent agronomists across southern Queensland and northern NSW, and this is how we would use this harvest to plan next year’s paddocks.
Why a dry finish brings it out
Crown rot is caused by a fungus, mostly Fusarium pseudograminearum, that survives in cereal stubble and grass weeds and infects the next cereal crop at the crown and stem base. Infection is high in a wet autumn and winter, but the symptoms above ground normally only show when the plant comes under water stress late in the season. That is when the whiteheads appear and the heads fill poorly.
The finish largely decides how much yield it takes. At a GRDC webinar last year, NSW DPIRD plant pathologist Steven Simpfendorfer said a paddock might lose about 3 per cent of its yield to crown rot in a kind season, and 55 per cent in a season full of stress, with the same level of inoculum.
That is why whiteheads are a poor measure of how much crown rot you have. They say more about how tough the finish was than how much fungus is in the paddock. Mice, insects and frost can cause whiteheads too, barley generally does not show them and oats rarely do, and in a good year crown rot can still take 5 to 10 per cent of the yield without whiteheads you would notice.
What it means for 2027
The fungus survives in cereal stubble for three years or more, and it keeps growing up standing stubble after harvest. Over a six-month summer fallow at two sites in northern NSW, the height it reached in standing stubble rose by 60 to 70 per cent. Stubble breaks down fastest in moist conditions, so a dry spell slows the decline. Where disease levels are high and rainfall is low, it can take two to four years before infected residue has broken down enough to bring the risk down to a level suitable for durum.
Inoculum can also build without much to see. Surveys across central and northern NSW showed crown rot building up from 2020 onwards, while the mild, wet finishes of 2021 and 2022 kept whiteheads down. How a paddock looked this spring is only part of the story.
How to check your levels now
The window for a visual check runs from grain fill until about a month after harvest, while the stubble is still standing. For each paddock:
- Walk a large W across the paddock and pull five plants at each of 10 spots.
- Pull back the leaf sheaths and look for a honey to dark brown colour at the base of the stems. You may also see white or pink fungal growth.
- Record the percentage of plants with browning.
As a guide for the next cereal crop, under 10 per cent of plants infected is low risk, 11 to 24 per cent is medium, and over 25 per cent is high.
Once the crop is off, you can also have the stubble tested in a lab. A government lab tests cereal stubble samples for crown rot free of charge.
Before planting, a DNA test on soil and stubble shows how much crown rot fungus is actually there. It needs its own sample, taken on the old cereal rows where you can see them and including pieces of stubble with the crown, so a sample taken for soil nutrition will not do. It has to go through an accredited agronomist, the lab runs these tests weekly from February to June, and results come back within about two weeks. It measures the fungus, not the season, so it will not tell you what spring will do, but it does tell you where the risk sits.
What to do about it in 2027
Crown rot is managed paddock by paddock. These are the decisions that matter:
- Crop choice. Losses are generally worst in durum, then bread wheat, then barley, then oats. Keep durum for the lowest-risk paddocks and avoid it where the risk is high. Barley loses less yield, but along with durum it builds up inoculum the most, and oats are not a break either.
- Break crops. Canola, pulses and summer crops do not host crown rot, but they are not equal. Inoculum falls most after dense-canopy crops such as canola, faba beans and field peas. Chickpeas are less effective at breaking down cereal stubble. In paddock testing across southern Queensland and central and northern NSW, 20 per cent of cereal paddocks following chickpeas had very high infection, against 7 per cent after faba beans. Cereals following a summer crop came up very high 41 per cent of the time, against 12 to 14 per cent after canola or a winter pulse.
- Break length. One year out may not be enough where levels are high, especially when a dry spell has slowed stubble breakdown. In the same testing, three cereal crops in a row gave a 50 per cent chance of very high infection. After a two-year break, only 19 per cent of paddocks came up high and 6 per cent very high. Keep the break free of volunteer cereals and grass weeds such as barley grass, ryegrass and wild oats, or it will not do its job.
- Variety. No cereal is resistant to crown rot, but tolerance varies a lot. In central NSW trials under high crown rot in 2023, wheat variety choice was worth up to 25 per cent in yield at one site and up to 118 per cent at another. Variety protects this season’s yield, not next season’s paddock, because it does not slow the fungus in the stubble after harvest. Check the current NVT disease ratings before you order seed.
- Inter-row planting. With accurate (±2 cm) GPS autosteer, planting between last season’s intact cereal rows cuts the number of infected tillers by around half, worth 5 to 10 per cent in yield.
- Stubble. Leave infected stubble standing and intact where you can. The fungus keeps growing up standing stubble, but the bigger risk comes when that stubble is knocked down and spread across the paddock by grazing, mulching, cultivation or the planting pass. Cultivation does speed up breakdown, but it costs moisture and time, and without enough of either before planting it increases infection in the next cereal. Burning only removes the fungus above ground, and only as well as the burn goes. It does nothing for what survives in the crowns below ground.
- Nitrogen and zinc. Match nitrogen to stored soil water. A bulky crop that runs out of moisture in spring is more exposed to the fungus. Deep soil testing for nitrogen before planting, with a stored water estimate, lets you set the rate to the water you have. Make sure zinc is adequate, because whiteheads can be worse in zinc-deficient crops, but zinc above the recommended rate gives no extra protection.
- Planting time. Planting earlier in the recommended window brings grain fill forward and can reduce the heat and water stress that brings crown rot out. Weigh that against your frost risk.
- Seed treatment. A seed treatment registered last year for crown rot suppression in wheat and barley adds a layer of protection for the crop. It does not replace paddock selection and rotation.
Where we can help
If you want to get a handle on your crown rot levels and what they mean for 2027, talk to us. We can walk your paddocks and check stem browning while the stubble is still standing, take stubble samples after harvest and send them to that lab, and build the results into your rotation, variety and nitrogen plans. The lab does not charge for the test, so you only pay for our time in the paddock and the freight.
Call us on 0484 058 231, or get in touch with Dawson Agriculture.
Sources: GRDC Tips and Tactics, Crown rot in winter cereals, northern region (2016); GRDC Grains Research Update papers on Fusarium crown rot (2024); GRDC podcast, Get on the front foot with crown rot (April 2025); Grain Central report of the GRDC crown rot webinar (April 2025); 2026 Queensland winter crop sowing guide; ABARES Australian crop report, September 2026; APVMA. This article is general information, not a recommendation for any particular paddock. Trial and survey figures come from the sites and seasons cited, and results on your farm will vary.
